Adjustable electrode spark gap assembly



May 26, 1970 6.11.0566 3,513,516

ADUSTABLE ELECTRODE SPARK GAP ASSEMLY Filed March 16, 1965 INVENTOR. HAMLDE EcKEp BY PETER A. 01m0- AT T ORNE Y United States Patent f vI 'ADJUSTABLEELECTRODE SPARK GAP Peter-,Af Oddo and Harold F, Becker, Red Bank, NJ., assignors, VlynrresneV assignments, to Signalite, Inc., Neptune, NJ., a corporation of New Jersey .S. .Cl. Z9-25.16 Y Y 3L Claims ABSTRACTjOF` THE DISCLOSURE A method of fabricatinga spark gap in which a movable electrode extends yrintorthe gap througha hollow tube and the spacing of the gap is set prior to exhausting and sealing otr the gap.

The present invention relates to electron discharge devices and more particularly to spark gaps and to the method of making thesarne.`

The breakdown voltage of spark gaps depends substantially upon the pressure-gap spacing relationship. Present sealing techniques are such that extremely close tolerances in gap spacing are diicult to maintain. This makes it necessary, in producing gaps which have close tolerances in spacing, to fill them individually to a predetermined breakdown voltage. Thus it is necessary to apply the predetermined voltage across the gap and allow the gas to enter until the discharge occurs.

The present invention provides a spark gap assembly which ycan be adjusted accurately to any spacing within a predetermined range after sealing in and prior to exhausting and filling. In accordance with the invention, a tight tolerance in the order of i001" can be maintained. Pressure can then be determined for a given gas and spacing of the electrodes, thus enabling a plurality of devices to be filled at one time on a system. All of the devices would be within a predetermined range of breakdown voltages.

It is an object of the invention to provide an improved electron discharge device.

Another object of the invention is to provide an improved spark gap.

Another object of the invention is to provide a novel method for fabricating a spark gap.

Another object of the invention is to provide an improved method of fabricating a spark gap in which the electrodes can be accurately spaced.

Another object of the invention is to provide a high volume, low cost method of producing spark gaps.

Another object of the invention is to provide a method of adjusting gap spacing in a spark gap having an opaque envelope.

The above and other objects and features of the invention will appear more fully hereinafter from a consideration of the following description taken in connection with the accompanying drawings wherein one example is illustrated by way of example.

In the drawing:

FIG. 1 is a sectional view of a device illustrating the invention.

FIG. 2 -is a sectional View of fixed electrodes for use in devices made in accordance with the invention.

FIG. 3 is a sectional view of adjustable electrodes for use in devices made in accordance with the invention.

FIG. 4 is a diagrammatical view of a typical adjusting device.

Referring now to the drawing, a spark gap is indicated generally by the numeral 5 and includes an envelope 6 of a suitable material such, for example, as glass. It is understood, however, that other material could be used 2 for the envelope. A fixed electrode 7 is` sealed in one end of the envelope 6 by a glass to metalseal 8.The elec# trode 7 includes a stem section 9-of a hollowmetallic rod of a suitablevmateriahvfor example, `a nickel-ironcobalt alloy commonlyknown as Kova1'.I Attached to the stem section 9 by welding or any other suitable'manner is an electrode section10 of a suitable material, for example, a refractory metal.v I t is understood that the electrode section could lbe of other configuratiouthan that shown, as an example, it could be similarto that shown in FIG. 2 as 1 0A. Other configurations could also be used. An opening 11 is provided in the stem '9 vto permit exhausting and filling the envelope with a suitable gas. An exhaust tubulation 12 is attachedto the stern? iuaconventional manner. `v i An adjustable electrode assembly 13 is, sealed in the otherend of the envelope 6 by a glass to metal seal 14. The assembly 13 includes. a hollow tube 15 .of a suitable material, for example, Kovarf Inserted in the tube 15 is a rod-like stem member 16, which may be of the same material as the tube 15. Normally the stem member Y16 will have an O.D. slightly less than the I.D. of the tube 15, for example .00 Attached to the stem memberl by welding or in any other manner is an electrode member 17 of a refractory metal. The configuration of the electrode 17 may be those illustrated in FIG. 3 or any other suitable configuration.

The spacing between the fixed electrode 10 and the hollow tube 15, the distance A of FIG. l, for spark gaps to cover a predetermined range is proportioned so that when the adjustable electrode 17 is pulled back all the way, the gap spacing, the distance B of FIG. 1, will be suicient to provide for the maximum required breakdown for the predetermined range. The length of the stem 16, the distance C of FIG. 1, is proportioned to permit suicient movement of the electrode 17 to obtain the minimum gap spacing required in the predetermined range.

The devices as set forth above may be made in quantities large enough to warrant an automatic sealing set up and to be stocked. When gaps having certain predetermined characteristics are desired, the spacings are adjusted on an appropriately accurate measuring device to the correct gap spacing to provide the predetermined characteristics. The tube 15 is then crimped to fix the stem 16 and thereby the gap spacing B. The excess of the tube 15 and stem 16 is then cut off and a hermetic weld made between the tube 15 and stem 16. The device is then exhausted and filled to a predetermined pressure of a suitable gas or mixtures of gas and then tipped and sealed ofi.

Reference is now made to FIG. 4 wherein one embodiment of a gap positioning device is illustrated. A11 adjusting fixture is indicated generally by the numeral 20 and includes a base 21. Mounted on the fbase 21 isa pair of clamps 22 adapted to receive the device 5 and to hold the same in a fixed position. Also mounted on the base 21 is a micrometer adjusting screw 23 adapted for engagement with the rod 16 of the adjustable electrode assembly 13, thus permitting micrometer adjustment of the electrode spacing B.

Although only one embodiment of the invention has lbeen illustrated and described, various changes in the form and relative arrangement of the parts, which will now appear to those skilled in the art, may be made without departing from the scope of the invention.

What is claimed is:

1. A method of fabricating a spark gap comprising the steps of sealing in a fixed electrode in an envelope, mounting a movable electrode on a rod-like member, placing said rod-like member in a hollow tube, sealing said hollow tube in said envelope with said' movable elec- "Patented Mayas, i970 electrode is fixed-"and sealed to said 'tube by Vcrimping said 2,422,465' 5/1'947 "31'3*`286 X hollow tube onusa'idl rod-like member and" weld-sealing 2,424,805 7.,/1947. -1-713132-86x saidJtubevmd rriierriber` to one another. `A 214511184: 1Y0/1948, V f.- 3.13j253 X v3. -A method-'of fabricating a'spark gap having a pair 21456896. 12/ 1948 A, 313,.*2767 X of,e'lectrod'esf enclosed in an envelope comprising ,the 2,817,036," :l2/19577,. 313-146 steps of mountingone of said'electrode's on one end of 2,923,798 2/1960 Y 313-266X a hollowfstem, sealing/said hollow stern in one end of l 3,048,681 8/1962 Polmko 313'7252' X said envelope, connecting'the other endA fv said stem to Ian exhaust vtubulation, fmonnting the other of said elec- Y' trodes on a ro'd-lilmember, inserting said rodLlike mem- ,t FQREIGN 'PATENTS n ber in'ahollowftuibe, Sealing said hollow tube in the other 119,785 4/1945 Australia.A j

end of said envelope, Vadjusting the spacing between said ,y 126,873 3*/1948 Australia. v

electrodes to a predetermined value byl moving said vrod- 410,253 3/1945` Italy.

like member inv said tube permanently, securing said other f 1 f electrode in a fixedy position in said hollow'tube by crimp- JOHN W. HUCKERT, Primary. Examiner ing andfweldvin'g said hollow tube and said rod-like memj -R SHEWMAKER` AssistanbEXaminerber to form an hermetic seal external of said envelope p v 3 betweensad rod-like member and said hollow tube, 5 Us C1' vXR 4 exhausting'and filling said envelope to a predetermined V Y t 313-146, 214, 253, 285', 325; 31e- 22 p i 3,229,145 1/1966 Jensen 313-253 X pressure of a gas, and tipping off and sealing said hollow stem. 

